When Dan Reeves moved the Rams from Cleveland to Los Angeles in 1946, the owner made a prediction about his new home.

“It’s going to be the greatest professional football town in the country,” Reeves said.

Seventy-one years later, the boast about the nation’s second-largest market remains an open question.

With an early-morning announcement Thursday, the Chargers ended 56 seasons in San Diego and joined the Rams in L.A. After the NFL’s 21-year absence from the region, two teams have returned in the space of 365 days to an area already crowded with college and professional sports options.

Though the NFL has long been steadfast in its public belief that L.A. can support two teams, there is unease in private. Some in league circles believe the Chargers made a hasty decision to move. As the NFL’s television ratings plunged this season, there is also concern the addition of a second struggling team could saturate a market that’s already lost three franchises.

“L.A. has a well-earned reputation for being a community that over-supports front-runners and under-supports teams that don’t do well,” said Marc Ganis, president and founder of the Chicago-based sports consulting firm SportsCorp. “Frankly, I have meaningful doubts about L.A. supporting two teams with sellouts unless both become very successful on the field.”

Victor Matheson, a sports economist at College of the Holy Cross in Massachusetts who has studied the NFL, was blunt.

“L.A. isn’t a risky market,” he said. “But it becomes a risky market when you add a second team.”

The issue is attention, not population or money. Even for the nation’s most popular league, standing out in a sprawling, easily distracted region already loaded with professional baseball, basketball, hockey and soccer teams — in addition to USC and UCLA — isn’t a given.

Though the Rams received more than 45,000 season-ticket deposits in the first 48 hours they were available last year — and averaged 84,456 fans a game at the Coliseum — the excitement soon faded into the dreary reality of a 4-12 season and an awkward divorce from coach Jeff Fisher. Television ratings drooped and empty seats were a familiar sight at the Coliseum by season’s end.

The one thing you can never do in L.A, rapper and filmmaker Ice Cube noted in his 2010 documentary on Al Davis and the Raiders, is lose.

The first love is normally the team that impresses with playoff wins and championship victories. Think Dodgers, Raiders, Lakers, Kings, Galaxy.

Runner-ups may have some playoff appearances, perhaps a single championship, but they normally can’t capitalize on it. Think Angels, Rams, Clippers, Ducks, the now defunct Chivas USA (to be the new 2nd LA MLS team)

The top teams tend to remain the top teams, the runner-ups the dalliance option.

The Chargers have a much higher probability of making the playoffs here in L.A., not the Rams.

So a 2nd team moving to L.A. is good, but not for the Rams.

If you’re sitting here reading this and wondering why I never mention USC or UCLA: college teams don’t factor into the equation. Alumni loyalty counts for more in tickets sales than a winning record. Colleges don’t have the option of picking up and moving locations.